(a) Field of the Invention
The present invention relates to a vehicle motor, and more particularly to a brushless motor for use in a motor bicycle which minimizes vibration and cogging torque during rotary motion of the rotor.
(b) Description of the Prior Art
Regular bicycles are used as sports equipment or short distance transportation vehicle means. Because riding a bicycle consumes much effort, a bicycle is not suitable for use as a long distance transportation vehicle. In recent years, various motor bicycles have been developed for use as practical transportation vehicle means. U.S. Pat. No. 5,581,136 teaches the use of a vehicle motor in a bicycle. Various brushless motors have been disclosed for use in motor bicycles. However, these brushless motors, still do not satisfactorily function because they cannot eliminate a cogging torque. These brushless motors commonly comprise a stator and a rotor. The rotor comprises a plurality of equiangularly spaced magnets. The stator is comprised of a silicon steel stack having a plurality of T-teeth around the periphery, and a winding mounted on the T-teeth. The number of the T-teeth is a common multiple of the number of the magnets at the rotor, or equal to the number of the magnets. When one magnetic pole of the rotor is aligned with the center of the magnetic field of one magnetic pole of the winding at the stator, a dead angle is produced, causing the rotor to vibrate. For example, if the number of T-teeth of the stator of a two-phase motor is 4, the rotor has N pole and S pole, and a dead angle is produced when upon each 90.degree. rotation of the rotor. If the number of T-teeth of the stator of a three-phase motor is a common multiple of or equal to the number of the magnets at the rotor of the rotor, a cogging torque will be produced when starting the rotor. This drawback shortens the service life of the motor, and affects the performance of the motor. During operation of the motor, high heat may be produced, causing the related Hall ICs to be burned out.